Heterodyne receiving system



Feb. 13, 1934. w .RUNGE 1,947,229

HETERODYNE RECEIVING SYSTEM Original Filed Nov. 6, 1925 INVENTOR WiLHELM RUNGE ATTORNEY Patented F b. 13, 1934 UNITED STATES nn'rmonrms RECEIVING svs'mm Wilhelm Runge, Berlin,

,amignorto Germany 'I'elefunken Gesellschaft fiir Drahtlom Telegraphie mit besehrinkter liaftung, Berlin, Germany.

application November 6, 1925, Serial No.

67,206, now Patent No. 1,890,302, dated December 6, 1932, and in Germany November 15, 1924.

Serial No. 629,837

Divided and this application August 22, 1932.

6 Claims. (Cl. 250-20) The object of the present invention, which is a divisional application of Serial No. 67,206, filed November 6, 1925, and resulted in U. S. Patent No. 1,890,302 on December 6, 1932, is to provide means whereby the differential beat frequency resulting from two oscillation circuits is kept constant during equal changes in tuning means.

A further object of the invention is to provide means whereby at a single setting, for instance,

10 the turning of a knob or handle, the beat frequency of two cooperating oscillation circuits preserves a constant magnitude.

Other objects of the invention will appear more fully hereinafter as shown in the accompanying drawing, and finally pointed out in the appended claims. I

The novel features. which I believe to be characteristic of my invention are set forth in particularity in the appended claims, the invention itself, however, as to both its organization and meth-' 0d of operation will best be understood by reference to the following description taken in connection with the drawing in which I have indicated diagrammatically one arrangement whereby my invention may be carried into efiect.

Referring to the drawing, I

Fig. 1 shows an embodiment of an arrangement conformable with the present invention,

Fig. 2 is a diagram showing a graph wherein the dependence of the resonance frequency of an oscillation circuit upon the reciprocal value of a capacity and their functions is exhibited.

Fig. .3 is a diagrammatic sketch wherein inductance values are substituted for the variable capacity,

' Fig. 4 shows the means able condensers.

In connection with the service work and the various problems encountered in high frequency 40 work it is often essential that the difference in frequency of oscillations of two high frequency circuits should be kept constant over variable wave ranges. A change from one wave range to another wave range ordinarily requires separate setting of tuning means in each of the twovcircuits. In many cases separate adjustment of the tuning means in each of the circuitsis rather tedious and inconvenient.

One of the problems for adjusting the varito be solved by the present invention is that by a single setting as for example the turning of a knob or handle as set forth above the beat frequency of two oscillation circuits, which may be varied, is maintained constant. An illustrated embodiment ofthe invention consists 5 in that one of the two oscillation circuits is an inductance and a condenser of the rotary type,

and the other oscillation circuit is an inductance of somewhat lower value, a rotary condenser, and a fixed condenser in series with the latter. It can be proved that with a proper proportioning of the circuits, a synchronous turning of the two condensers or other tuning elements may be made to yield a differential beat whose frequency remains appreciably constant. The circuits shown in Fig. 1 illustrate a self-inductance L1 and a capacity Cv while the other circuit possesses a selfinductance of lesser value L2 and a capacity which is determined by the series connection of the two condensers with capacities Cv' and Cs.

In Fig. 2 the dependence of the resonance frequency of an oscillation circuit upon the reciprocal value of capacity (see curve 1) is shown. This curve, as is well known is the parabola. If in the same graph the dependence of frequency on C, is plotted for the case where the oscillation circuit contains in addition the series capacity Cs, there results a displacement of the parabolic curve along the abscissa by an amount as shown by curve 2.

The shape of the parabola (its focal distance) depends itself upon the value of the self-inductance which represents the parameter. Hence, by a convenient selection of the self-inductance, it is easy to change curve 2 into curve 3. Curve 1, therefore, representsthe frequency depending upon the change in capacity in an .oscillation circuit such as circuit 1 in Fig. l, andcurve 3 shows the frequency dependence of an oscillation circuit corresponding to circuit 2. Fig. 1, upon the analogous setting of the corresponding rotary condenser in this circuit. Hence, the relation holding for the circuit 1 is and t e relation for circuit 2 is As can be inferred from numerical examples and as diagrammatically-shown in the graph, the difference of the frequencies of the two circuits inside a frequency range lying approximately be-v two condensers upon a common axis or spindle and to vary the tuning in the two circuits by turning one knob in such a manner that the difference of their frequencies remains well nigh unvaried.

Fig. 4 shows the two variable condensers Cv and Cv' having their movable plates 6 and 7 mounted upon a common spindle 8 which is provided with an adjusting knob 3 at one end for simultaneously adjusting the condensers.

A corresponding result is attainable also by other means, for example, in one of the circuits i. a variometer L1 is exhibited in lieu of a rotary condenser, and instead. of the fixedself-inductance coil there is used a fixed condenser C1. Also in-circuit 2' in lieu of the series connection of the fixed and the variable condenser a parallel connection is substituted consisting of low and'high self-inductance L3 and L2. In an arrangement of this kind the functions of L and C are exchanged as can be seen by comparison of the relations between the two circuits. The

dotted line 8' represents a common spindle for simultaneously adjusting the adjustable elements of variometers L1 and L2.

A very important application of the present invention is in heat reception arrangements, for instance, telephone reception apparatus working with. intermediate beat frequency. One of the -oscillation circuits in this case is the circuit to which the incoming high frequency oscillations are supplied while the second circuit is the oscillation circuit of the local high frequency generator whose oscillations are superposed upon the incoming high frequency oscillations, rccti-- fication of the oscillatory currents being then made.

By a single adjustment it is then possible to efiect the tuning of the radio receiving circuit as well as to maintain constant the beat frequency of the intermediate ordifferential frequency.

What I claim is: V 1. In a heterodyne receiving system, the combination of a receiving circuit and a local oscillation circuit, one of said circuits including a condenser, a fixed inductance and a variable inductance and the other of said circuits includ-,

ing only a condenser and an equal variable inductance, said variable inductances being of sub stantially similar characteristics throughout the range of variation, and common means for adjusting said variable inductances by equal amounts, the values of said fixed and variable 7 inductances being so related that a beat fre quency of substantially constant value .is pro duced by adjustment of said variable inductances. the condenser in one of said circuits being greater than the condenser in the other.

2. In a heterodyne receiving system, a receiving circuit including only a condenser and a va-- riable inductance, alocal'oscillation circuit coupled to the receiving circuit including a condenser, a fixed inductance and a. variable inductance connected together, the inductances of said tion circuit, one of said circuits including a condenser, a fixed coil and a variable coil and the other circuit including a condenser and a variable coil substantially equal to said first named variable coil, both said variable coils being of substantially similar characteristics throughout the tuning range and a single control means for adjusting said variable coils by equal amounts, said fixed and variable coils having such relative values that a high intermediate beat frequency of substantially constant value is produced by adjustment of said variable coils through a limited tuning range, the capacity in one of the circuits being greater than the capacity in the other.

4. A superheterodyne receiver for telephone signals, comprising a receiving circuit including a. condenser and a variable inductance, a local oscillation circuit coupled to the receiving circuit including a condenser, a fixed inductance and a variable inductance connected together, the

inductances of said variable inductances being equal and said variable inductances being equally adjusted by one control means, said-fixed and variable inductances having such relative values that an intermediate beat frequency of approximately constant value is produced as the receiving circuit is tuned to an incoming signal by said control means, the ratio between said condensers having a value other than unity.

5. A superheterodyne receiver comprising a receiving circuit including a condenser and means providing aivariable inductance, said circuit being designed tobe tunable over a frequency range by said variable means, a local oscillation circuit coupled to the receiving circuit including a condenser and. a variable inductance, said oscillation circuit being designed to be tunable over a different frequency range by its variable inductance, the inductances of, said variable inductances' being equal, a single control means for adjusting said inductances between substantially their minimum and maximum inductance positions by equal amounts, the frequency difference between said circuits as said single control is adjusted being a variable, and a fixed inductance connected to the variable inductance of said oscillation circuit of such value with respect to the variable inductances of both circuits that said frequency difference is automatically maintained substantially constant as said single control is adjusted between said positions.

6. A superheterodyne receiver comprising a receiving circuit including a condenser and means providing a variable inductance, said circuit being designed to be tunable over a frequency range by said variable means, a local oscillation circuit coupled to the receiving circuit including a con- .denser and a. variable inductance, said oscillation circuit being designed to be tunable over a different frequency range by its variable inductance, the inductances of said variable-inductances being equal, a single control means for adjusting said inductances between substantially their minimum and maximum inductance positions by equal amounts, the frequency difference between said circuits as said single control is adjusted being a variable, and a fixed inductance connected in shunt with the variable inductance of said oscillation circuit of such value with respect to the variable inductances of both circuits that said frequency difference is automatically maintained substantially constant as said single control is adjusted between said positions. WILHELM RUNGE.' 

